Hydraulic Conductivity from Nuclear Magnetic Resonance Logs in Sediments with Elevated Magnetic Susceptibilities. Issue 3 (30th December 2021)

• Record Type: Journal Article
• Authors: Crow, Heather; Paradis, Daniel; Grunewald, Elliot; Liang, Xiao Xia; Russell, Hazen A.J.
• Is Part Of: Ground water. Volume 60:Issue 3(2022)
• Page Start: 377
• Page End: 392
• Publication Date: 2021-12-30
• Subjects: Groundwater -- Periodicals; Wells -- Periodicals; Eau souterraine -- Périodiques; Puits -- Périodiques; Grondwater; Eau souterraine; Puits; Electronic journals; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 551.49
• DOI: 10.1111/gwat.13158
• Languages: English
• ISSNs: 0017-467X

Abstract

Abstract: This study examined the application of slim‐hole nuclear magnetic resonance (NMR) tools to estimate hydraulic conductivity ( K NMR ) in an unconsolidated aquifer that contains a range of grain sizes (silt to gravel) and high and variable magnetic susceptibilities (MS) (10 −4 to 10 −2 SI). A K calibration dataset was acquired at 1‐m intervals in three fully screened wells, and compared to K NMR estimates using the Schlumberger‐Doll research (SDR) equation with published empirical constants developed from previous studies in unconsolidated sediments. While K NMR using published constants was within an order of magnitude of K, the agreement, overprediction, or underprediction of K NMR varied with the MS distribution in each well. An examination of the effects of MS on NMR data and site‐specific empirical constants indicated that the exponent on T 2ML ( n ‐value in the SDR equation, representing the diffusion regime) was found to have the greatest influence on K NMR estimation accuracy, while NMR porosity did not improve the prediction of K . K NMR was further improved by integrating an MS log into the NMR analyses. A first approach detrended T 2ML for the effects of MS prior to calculating K NMR, and a second approach introduced an MS term into the SDR equation. Both were found to produce similar refinements of K NMR in intervals of elevated MS. This study found that low frequency NMR logging with short echo times shows promise for sites with moderate to elevated MS levels, and recommends a workflow that examines parameter relationships and integrates MS logs into the estimation of K NMR . Abstract : Article impact statement : Hydraulic conductivity estimates from nuclear magnetic resonance data are refined when using a workflow that integrates magnetic susceptibility logs.